Improving polyhydroxyalkanoates storage capacity of a mixed microbial culture fed with hardwood sulfite spent liquor

BACKGROUND: The development of sustainable industrial processes demands the recovery and transformation of their by-products. The production of polyhydroxyalkanoates (PHAs) by mixed microbial cultures (MMC) is one of the available routes. This study evaluated the possibility of applying a two-step PHAs production process using an industrial by-product, hardwood sulphite spent liquor (HSSL), as feedstock for a MMC. The first step consisted in the selection of PHAs-storing microorganisms using an aerobic dynamic feeding strategy followed by a second step, accumulation. RESULTS: The selected MMC, despite not being able to use the main carbon source of HSSL, lignosulphonates, revealed the capacity to consume acetate and xylose to accumulate poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and glucose biopolymer. The maximum PHAs content was relatively low, 6.6%, with a maximum production yield of 0.49 C-mmol HA C-mmol S−1 during the selection stage. CONCLUSION: A MMC was able to adapt to HSSL by consuming acetate and xylose. The imposed operational conditions resulted in a partial selection of the culture, since only acetate-consuming organisms experienced a real feast/famine regime, resulting in low PHAs production. © 2015 Society of Chemical Industry.